Brake mechanism



Patented May 11, 1937 UNITED STATES PATENT OFFICE BRAKE MECHANISM Samuel F. Arbuckle, Highland Park, 'Mich as-- signor to S. F. Arbuckle Corporation, a corporation of Delaware Application December 22, 1932, Serial No. 648,510

6 Claims.

ments in Brake mechanism of the present applicant and Andrew -L. Vargha, filed April 2, 1928, Serial No. 266,551, and in Letters Patent of the United States, No. 1,834,368, for Braking mechanisn, issued to the present applicant, December 1, 1 31.

The principal object of the present invention is to improve the construction and control of the above types ofbrake mechanisms.

Another object is to provide, in combination with a brake system and booster mechanism therefor, means controlled by suitable operation of the brake pedal'for varying the amount of brake pressure which the booster mechanism may exert upon the braking system and means controlled independently of the brake pedal for limiting the amount of such braking pressure.

Another object is to provide automatically adjusted means and independent manually adjustable means for controlling and limiting the effective power application of vacuum operated brakes.

Another object is to utilize the higher values of vacuum developed within the intake manifold of a vehicle motor in the operation and control of the booster system. i

A further object is to arrange mechanisms for controlling and limiting the power application of suction operated brakes so as to insure quick action of such mechanisms.

Other objects and advantages will become apparent fromthe following description-and ap--- pended claims taken in connection with the accompanying drawings which, for the purpose'of illustrating the invention, depict'several concrete embodiments thereof.

In the drawings:

Figure 1 is a more or less diagrammatic fragmentary perspective of "onearrangement of suction operated power means for actuating the brakes of a vehicle and the control mechanism for such means,

Fig. 2 is a more or less diagrammatic vertical section taken centrally through the control mechanism shown in Fig. 1, and illustrates manually adjustable and automatic means for varying the effect of the power operated means shown in Fig. 1,

Fig. 3 is a vertical section taken longitudinally whereby the maximum the various parts making up the conjunction with the through the center of a manually controlled member for controlling the eifective pressure that may be applied to .the power members in vacuum operated brakes,

Fig. 4 is a top plan of a modified form of the 5 control mechanism shown in Fig. 2, such mechanism being shown as supported on the transmission of a motor vehicle,

Fig. 5 is a vertical section of Fig. 4,

taken on line 55 Fig. 6 is a more or less diagrammatic perspective of a portion of an automobile chassis showing the application of a booster mechanism and control apparatus therefor to a hydraulic brake system,

Fig. 7 is a more or less diagrammatic vertical section of the booster mechanism and control apparatus therefor shown in Fig. 6, and

Fig. 8 is an enlarged detail of the valve mechanism shown in Fig, 2.

In the application of power operated brake mechanisms to motor vehicles, it is desirable to permit the maximum braking efiort that may be applied by the braking means to be. easily and quickly varied, plication of the brake will be prevented under conditions where such excessive application is hazardous such as, for instance, on wet or icy roads. The present invention contemplates the provision of a manually controlled mechanism,

braking effort that may be applied, by so-called vacuum or suction operated brake mechanisms may be easily and quickly adjusted so as to prevent the wheels from locking under varying conditions of road surface. The invention also contemplates the provision of novel forms of control means for controlling-the application of-such power actuated braking means, the advantages resulting from which will be apparent from the following description and explanation. The present invention further con templates the provision of a braking system which, by means of its construction, lends itself to application to various requirements as to braking effort without change in construction of I power system, which is-commercially desirable. The invention further contemplates the provision of means for utilizing the higher values of vacuum developed in the engine intake manifold in the operation and control of the'booster system employed in braking system and further contemplates the provision of means for limiting the application of the power actuated whereby an excessive power apbraking means so arranged as to provide quick action of such limiting and controlling means.

- is provided with a downwardly extending lever ends are constrained to equal movement.

l4 -at-each end thereof and each lever I4 is connected by a rod 5 to the brake on the corresponding rear wheel (not shown) of the motor vehicle. The shaft II is also provided with an upwardly extending lever H! which is connected by a rod l9 to one of the levers |2 on the front cross shaft Ill so that rocking of one of the shafts ||l or II will cause a corresponding rocking movement of the other shaft. The free end of one of the levers I4 is connected by a rod 20 to the foot operated pedal 2| which will be described later more in detail. Upon depression of the pedal lever 2 the shaft I is caused to rock and causes a like rocking movement of the shaft I0 and consequent manual application of all of the brakes.

In the provision of power means for applying the brake, two bellows l6 and H are employed, the bellows l6 being considerably larger'in diameter than the bellows |1. Both bellows are mounted in a rigid frame 22, at opposite ends thereof, and their adjacent ends are connected by a rod or other member 23 so that their free A lever 24 pivotally mounted to the upper edge of the frame 22 is slidably connected intermediate its length to the rod 23 and its free end is connected by the rod 25 to the lever 26 secured to the shaft II, the connection between the rod 25 and lever 26 being of the lost motion type. The interior of the bellows I1 is in constant communication with a. source of suction through the conduit 21 and the interior of the bellows I6 is connected by the conduit 28 to a control mechanism mounted on and controlled by the foot pedal 2|, the con-' trol mechanism being indicated generally at 30 and being connected to a suitable source of suction such as the intake manifold 3| of the internal combustion engine 32. In this construction, both bellows 6 and H are normally held under a suction or partial vacuum when the brakes are in inoperative position, tne effect of this is that the vacuum being equal in both bellows, the-larger bellows |6 collapses and,over comes the collapsing tendency in the smaller bellows |1, causing. the smaller bellows to be held in extended position even though it is under a partial vacuum. In this position the brakes are held in inoperative position and when the control mechanism 30 is suitably actuated, air is admitted to the larger bellows I6 which thereby. breaks the vacuum in the same and permits it to ex-' pand and the smaller bellows H to contract, thus moving the connecting member 23 forwardly and rocking the lever 24, which rocking movement is transmitted by the rod 25 and lever 26 to the shaft II and causing subsequent application of all the brakes. The advantage of this mechanism is that a quick application of the brakes may be mightinterfere with carburetion of engine '32;

Upon release of the control mechanism 30, as

is again-connected to the suction source and is caused to collapse, thus releasing the brake.

Referring more particularly to Figs. 2 and 8,

there is shown in greater detail the control mech- I anism for the bellows l6 and I1 illustrated in Fig. 1. The control mechanism, designated generally at 30, as above indicated, comprises a housing 33 mounted on the' forward face of pedal lever 2| and closed at its lower end. Slidably received within the housing 33 is a sliding member 34 having a passage 35 therein. A spring 36, held in compressed condition between the lower end of the member 34 and the closed end of the housing, normally urges the member 34 upwardly. The member 34 is provided with a stem 31. A pedal pad 40 is pivotally mounted at 38 on the free end of the pedal lever 2| and is provided with is held by pressure applied to the lower edge thereof against a stop 44 on lever 2|, or pad 40 may be rocked without rocking the lever 2| on the shaft 43, or the pad 40 may be rocked simultaneously with the lever 2|. If the pedal pad 40 is rocked by pressure applied to the upper edge of the same, the foot 42 will be moved in the general directionof the axis of stem 31 and will act through this stem to urge the member 34 downwardly into the housing 33 against the pressure of the spring 36. When the member 34 is in normal inoperative position in the housing 33, the passage 35 is connected by a passage 45 in the wall of the housing 33 with a conduit 23 which leads to the interior of the larger bellows I6. The passage 35 is also connected by a passage 46 with the conduit 41 which leads to a fitting 48 interposed in the suction line 21. Suction line 21, as previously pointed out, extends between the interior of the smaller bellows l1 and a source of suction such as the intake manifold 3| of, internal combustion engine 32. released position as indicated in Figs. 1 and 2, both bellows l6 and H are subjected to the suction of the system and the larger diameter bellows I6 is in collapsed condition effecting the release of the brakes. ,When the member 34 is With the pad in' between the interior of the housing and the atmosphere, so that the interior of bellows I6 is open to the atmosphere through conduit 28 and passages 35 and 49. The admission of air to the bellows I6 allows this bellows to expand while the bellows |1 still communicates with the suction system and is caused to collapse thus applying the brakes. Y

The-braking power developed by the suction in the above manner may be augmented by manually pressing the brake pedal 2| forwardly while the pad 40 is held in its tilted position relative to the pedal lever. When the brake pedal is released the pad 40 is rotated to its initial position against stop 44 by the action of spring 36, .the foot pedal re turning to its normal rearward position illustrated. The spring 36, in returning the pad 40 to its retracted position, moves the valve 34 upwardly, cutting off the admission of air to the bellows l6 and subjecting both bellows i6 and H to the suction of the system.

In order to prevent an excessive application of the booster mechanism to the brakes, and to control the amount of force exerted by the booster mechanism in accordance with the relativeposition of the brake pedal, the following mechanism is provided.

A small housing 50 is connected into the suction line 21 between the fitting 48 and the intake manifold 3 I, so as to be equally applicable to both be]- lows I6. and I1. This housing is provided with an opening leading to the atmosphere, and between the opening 5i and the point of entrance to the suction line 21 into the housing 5|], a valve seat 52 is formed. A valve 53 is adapted to rest against the seat 52 and is provided with an upwardly extending stem 54. Adjacent its top the stem is provided with a pin 55 secured against relative axial movement with respect to the stem and against which a washer 56 bears; A coil spring 51 encircles the stem 54 and is held under compression at all times between the washer 56 and a second washer 58 encircling the stem 54 and axially slidable thereon. It will be apparent that further compression of the spring 51, through pressure applied to washer 58, controls the point at which the suction within the line 21 will cause the valve 53 to open, and that the valve 53 upon opening will allow air to be drawn into the housing through the opening 5| and thereby prevent a a higher degree of suction from being built up in the suction line 21, and consequently will limit the suction that may be applied to either or both of the bellows I6 and I1. I

The compression of the spring 51 iscontrolled in the following manner. A'cam 59 is rotatably mounted on the shaft adjacent one side of the lever 2|. Pivotally connected to the cam 59 by the pin 68 is a ratchet segment 6| provided with a manually engageable lever .62. The free end of the segment 6| is normally urged outwardly by a'coii spring 63 held under compression between the same and the cam 59. The lever 2| is provided with a pin 64 which is adapted to engage one of the teeth on the ratchet member. 6| thereby locking the cam 59 in rotatably adjusted position relative to the lever 2|. The rotatable position of the cam 59 relative to the lever 2| may be varied by depressing the arm 62 so as tocompress the spring 63 thereby drawing the segment 6| out of engagement with the pin 64 after which the cam may be rotated to the desired position and the arm 62 released, causing the segment to again engage the pin 64. bracket 65 extended from the housing 50 are a pair of oppositely extending levers 66 and 61,'the free'end of lever 66 being normally held against the cam 58 and the free end of the lever 61 supporting the washer 58 on .the valve'stem 54. A flat spring 68 secured'to the lever 61 contacts with the lever 66, and upon clockwise rotation of the lever 66 about the pin 65, urges the lever 61 to a like movement but permits the lever 66 to move independently of the lever 61 when sufiicient pressure is exerted on the free end of the lever 61 to overcome the force of the spring 68. The cam 59 provides a cam surface so arranged that as the 'pedal 2| is depressed, the free end of the lever 66.

is moved downwardly thus moving the free end of the lever 61 and the washer 58 upwardly and tending to compress the spring'51 so that a greater suction must be present in the bellows I6 and I1 before the valve 53 will lift and limit such suction. This provision of means for manually adjusting the rotatable position of the cam 59 permits the adjustment of the mechanism so that a predetermined movement of the lever 2| will always exert a predetermined braking pressure on the brakes atmosphere through passages 84.

Pivotally mounted at 65 on a a regardless of the amount of wear on the brake bands. As the brake bands wear the cam 58 may be shifted to compensate for such wear] Referring particularly to Figs. 1 and 3, manually adjustable means provided for limiting the amount of braking effort which the bellows I6 and I 1 may apply in order to correspond with the condition of the road surface over which the vehicle may be traveling, will be described. This means may be in the form of a suction operated regulating valve, which may be mounted on the instrument panel, dash, or other suitable supporting surface 68 of a motor vehicle, in a position to be readily accessible to the operator. Inthe preferred construction of this valve, a flange-like member 1| is provided with a rearwa'rdly extending body portion'12 provided with an opening 13 at its forward end which opens on. the face of the flanged portion 1| and in the forward end of which is rotatably received the sleeve 14 of the handle 15. A portion of the wall of the body portion 12 surrounding the opening 13 is removed, as indicated in Fig. 3, and received .within the open-- ing I3 is a sleeve member 16, the forward end of which threadably engagesthe inner surface of the sleeve portion 14 of handle 15. The sleeve 16 is provided with a pair of outwardly projecting fingers 11 which prevent rotation of the sleeve 16 in the opening 13 and also serve as abutments 12. Thus, by turning the handle 15, the sleeve 16 is caused to move axially either one way or the other, depending upon the direction of rotation of the handle 15. The rear end of the body portion 12 is provided with a chamber 19 formed by drilling out the same and then plugging it. The chamber 19 may be connected by a connection 86 and conduit 8| with the suction line 21 extending between the brake-applying bellows and the source of suction previously described. The body 12 is-also provided with a chamber 82 connected with the chamber 19 and normally closed by the valve 83. The chamber 82 is connected with the The stem of the valve 83 slidably extends into the opening 13 through the closed end ofthe sleeve 16 and is provided at its free end with a nut 85. A coil spring 86 is held under compression about the valve stem between the nut 85 and the closed end of sleeve 16. When the suction within the conduit BI and suction line 21 becomes sufficiently great, the valve 83 is lifted from its seat, thereby admitting air into the conduit 8| through the passages 84 and the chambers 92 and 19 and pre venting greater su'ctionfrom being obtained than that for which the regulating valve is set. The degree of suction necessary to lift the valve 83 from its seat is, of course, controlled by the com pression of the spring 86 and this compression is,

. in'turn, controlled by the relative position of the closed end of the sleeve 16 with respect to the nut 85. Inasmuch as this relative position of the closed end of the sleeve 16 iscontrolled by the rotative position of the handle 15, it is readily apparent that by rotating the handle 15, the amount of suction which may be applied to operate the brakes'may be controlled. Thus, by rotatingthe handle 15in one direction, the compressionof the spring 86 will be decreased, thus permitting the valve 83 to unseat at a relatively small value of suction in the conduit 8I'and suction line 21, and

thereby limitsthe amount of braking-effort which may be applied bythe connected bellows I6 and I! to a relatively small amount, such as,' for instance, an amount commensurate with that necessary to apply the brake of a motor vehicle on an icy pavement without causing the wheels to slide. Conversely, if the handle 342 is rotated in a reverse direction, the spring 89 will be placed under a greater tension which will consequently allow a greater suction to be built up in the conduit 8| and in the suction line 21 before the valve 83 lifts and limits the degree of suction. In this manner, the effective maximum braking effort which may be applied to the brake by the bellows may be easily, quickly and readily controlled by simply rotating the handle I to the desired positionin order that the braking effort of the braking mechanism may be varied to correspond with the condition of the road surface over which the vehicle may be traveling. A check valve 81 is inserted in the suction line 21 adjacent the manifold 3|. This valve may be of any conventional design and serves to maintain the suction within the booster system at a. higher average level than would be obtained if the suction system of the booster mechanism were constantly in direct communication with the intake manifold. As the speed of engine 32 increases up to a certain point, the suction within intake manifold 3I also increases, but this suction drops off as the speed of the engine increases above this point. By providing the check valve 81 within the suction line adjacent the intake manifold (M, the value of the suction within the suction system'of the booster mechanism is maintained at a level approximately equal to the maximum value of suction produced within the intake manifold. Thus, more efficient and more constant operation of the booster mechanism are obtained.

It is also to be noted that in the above construction the means for limiting the maximum available braking effort that may be applied by the booster mechanism, which includes the valve 83 contained in housing I2 connected by conduit ill to the suction line 21 and the means for controlling the braking effort which may be applied by the booster mechanism in accordance with the depression of pedal lever 2I, which includes the valve 53 contained in housing 50 connected to the suction line 21, are both connected to or in the suction line at points adjacent the intake manifold of the engine but between the check valve 81 and the bellows I6 and II. By connecting these control units adjacent the source of suction, the control units will accurately determine the braking effort which may be applied by the booster mechanism at all times regardless of any leakage or other causes of loss of suction within the suction system of the booster mechanism.

Referring particularly to Figs. 4 and 5, a control device similar in effect to the control device shown in Fig. 2, for controlling the degree of suction or vacuum on the brake operating bellows, is illustrated. In this construction, a housing member 95 is shown secured to the side of the transmission housing 99 of a motor vehicle, although it may be secured to any other suitable supporting member.- The housing 95 is provided with a cross shaft 91 which rotatably receives thereon the lever 98, the lower end of which is yoked and on which is slidably received the rod 99, which may'correspond to the rod 20 shown in Fig. 1 and which is connected to the brake pedal, or may be any other rod pivotally or otherwise =secured relative to the brake pedal so as to be given axial movementupon depression of the through the opening H3.

brake pedal. Secured against relative rotation to the shaft 91 on the outside of the housing 95 is an arm member IN, the arm I02 of which is bent inwardly, as illustrated in Fig. 4, and normally held against the arm 98 by means of a coil spring I03.- Within the housing 95 and secured against relative rotation, is a third lever I04 provided with a yoked lower end. A lever I04 is provided with a finger I05 which is adapted to engage the adjustable screw I06 in order to limit the movement of the lever I04 in one direction. The housing 95 is provided with a chamber I01 which is connected by the conduit I08 to any one of the passages between the suction. source and the brake operating bellows. Preferably the conduit I08 connects the chamber I01 as close to and as directly to the source of suction as possible. The chamber I01 is connected by passage I09 to a chamber I I I in the housing 95 which is closed by a cover H2 and is connected to the atmosphere Com'PunIcation between the chambers I01 and III is normally prevented by means of a valve II4. A stem H5 ing 95 and is positioned centrally of the forwardly extending cylindrical portion III of the housing 95. The stem II5 passes through the lower yoked end of the lever I04 and extending forwardly from the valve H4. The forward end of the cylinder I I1 is closed by a fitting II8 which is centrally bored to provide a guide for the valve stem II5, the guide opening being vented at I20 so that pressure within the guide opening will not interfere with the seating of valve II4. Slidably received within the cylinder III is a sleeve II9 which is partially closed at one end as indicated at I2I. The coil spring I22 is held under compression between the end I2I of sleeve H9 and a washer I28 held against axial movement of the rod 99 and is preferably adjustably fixed axially of the rod. To adjustably fix the position of stop member I28 axially of the rod 99, a portion of the rod 99, at a point where it is easily accessible, is threaded as indicated at I29. A split nut I3I threadediy engages the portion I29 and may be locked in adjusted position by the lock nut I32. The nut I3I is provided with a splined portion I33 which is rotatably received within a similarly shaped end I34 of the sleeve I35 which encircles the shaft 99 and extends to and is secured to the stop member I28. Relative rotation of the sleeve I35 with respect to the rod 99 may be prevented by removing substantially half of the sleeve I35 for a material distance as indicated at I36 and inserting a pin I31 through the rod 99 so as to bear against the cut-away edges of the sleeve I35. By loosening the nut I32 and rotating'the split nut I3I, the axial position of the stop membei- I28 on the rod 99 may be easily and quickly adjusted.

In the operation of the control device shown in Figs. 4 and 5, as thusfar described, it will be apparent that when the brake pedal is depressed, the rod 99 is moved to the left and carries the stop member I28 with it. The stop member I28 acting against the end of the lever 99 rotates this The stop member 1 duit I08 communicates between the chamber I01 and there apply pressure to cause application of the compression of spring I22 is thus increased,

the suction..within the chamber 101 necessary to lift thevalve I I4 and release such suction, is increased accordingly. Upon continued movement of the rod 99 to the left, the arm I04 will continue to move the sleeve II9 until it comes-in contact with the fitting I I8 and prevents further compression of the spring I22. Any further movement of the lever 98 merely flexes the spring I03, the

arm I02 of the lever IIII moving out of contact with the lever 98. It will thus be apparent that any movement of the rod 99 to the left has the efiect of increasing the amount of suction which may be built up in the brake operating bellows and that the maximum amount of pressure which may be built up in such bellows is ultimately controlled by the axial position of the sleeve II9. It will also be apparent that by adjusting the position of the stop member I28 axially of the rod 99, the point at which increase in the compression of spring I22 begins, maybe controlled. Means for limiting the maximum effort which may be applied to the brakes by the bellows is provided and preferably takes the form of a suction operated valve such as that disclosed in Fig. 3. The housing 12 of such vacuum operated valve is connected to the chamber I01 by means of a conduit 8I.

The degree of suction required to operate this valve may be controlled by rotating the handle 15 to the desired adjusted position so that the suction opera-ted valve may be easily and quickly controlled by the operator of the vehicle. The conand a point in the suction line ofthe booster system adjacent a check valve 81 in a manner similar to that disclosed in Fig. 1. Thus, both the valve I I4 in housing I I6 and the suction operated valve in housing 12 are subjected to the suction within the suction line at a point adjacent the check valve so that quick operation of the control and limiting devices are obtained regardless of any leakage which may occur further back in the vacuum system.

Referring particularly to Figs. 6 and '7, there is shown the preferredarrangement of the present invention as employed in connectionwith a hydraulic braking system for a motor vehicle. In these figures, a conventional motor vehicle chassis frame I40 is provided with the usual wheels I4I. Mounted upon the engine transmission housing. I42 is a cylinder I43 usually known as the master cylinder, in which is received a piston I44, which is connected by a link I45 to the brake pedal I46 suitably mounted as upon the shaft I41 for oscillating movement. The master cylinder I43, which may be of any conventional design,

is connected to tubes such as l48 to the brake mechanism, indicated generally as I49 mounted for cooperation with each of the wheels MI. The brake mechanism I49 may take any of the conventional forms of mechanism of this type. In conventional operation,.when it is desired to apply the brakes, the foot pedal I46 is depressed, thereby moving the piston I44 in the cylinder I43 and causing the liquid therein to be forced through the I tubes I48 to the various brake mechanisms I49 the pedal I46, as well as the effective length of the pedal I46. For practical reasons this pressure is necessarily limited, and where such hydraulic braking systems are applied to motor vehicles 011 the truck or bus type, it is usually desirable, in

order to obtain the braking effort desired, to

provide means for applying a greater pressure to the liquid in the braking system .than is possible solely by foot pressure. Accordingly, a so-called vacuum booster mechanism may be employed to assist in the application of the brake mechanism.

This booster mechanism may include a. cylinder I55 which may be suitably mounted on the chassis frame I40 and in which cylinder a piston I56 is received. The piston I56 may be connected by a link such as I51 and lever arm I50 to a cross shaft such as I59 journaled at its ends in the opposite sides of the frame of the chassis, designated I40. The shaft I59 in turn maybe connected to the pedal I46 through a lever arm such as I60 and link I6I. The interior of the cylinder I55 is connected to conduits I62 and I63 to the intake manifold 3| of the internal combustion engine 32 which forms the motive power for the vehicle. A'valve mechanism is inserted between the conduits I62 and I63 in order to control the application of the suctionfrom the intake manifold to the cylinder I55. This valve, shown in detail in Fig. 7, comprises a housing I65 carried on an extension I66 of the foot pedal I46 in which a valve member I61 is slidably received. Extension I65 is provided with openings I68, I69.and I therein, the conduit I62 being connected with the opening I69, the'conduit I63 being connected with the opening I10 and the opening I68 being connected with the atmosphere. The valve I61 has a recess I1I in its lower side which bridges the openings I68 and I69 so as to connect the interior of the cylinder I55 with the-atmosphere when the valve is in an inoperative position. The valve I61 is controlled by a pad member I12 pivotally mounted on the foot pedal I46 at I13 and pivotally connected at I14 with a link I which is pivotally attached to a valve I61 at I16.

The pad I12 may be rocked about the pivot I13 independently of the movement of the foot pedal I46 to control the application of the booster mechanism through suitable movement of the valve I61. -When the pad is rotated in a counterclockwise direction from the position shown in Fig. 7, the valve member I61 is moved to. an operative position in which the recess -I1I bridges the openings I69 and I10 and thus connects the interior of the cylinder I with the source of suction. The suction, acting upon the piston I56, causes the latter to approach the closed end of the cylinder I55 and, acting through the link I51 lever arm I58, shaft I59, lever arm I and link I6 I, moves the foot pedal I46 towards the brakeapplying position. The braking power developed by the suction in the above manner may be augmented by manually pressing the brake pedal forwardly until the pad I12 is held in its tilted position. When the brake pedal'is released and the pad is rotated to its initial position, the brake partially-by the pressure in the system and partially by a spring I11 which is secured at one end to the frame of the chassis I48 and at its other end to the lever I58. The return movement of the pad I12 shifts the valve I81 bringing the recess I1I thereof into registration with the openings I88 and I89, thereby admitting air from the atmosphere into the cylinder I55.

In order to prevent an excessive application of the booster mechanism to the brake, and thereby to control the amount of force exerted by the booster mechanism relative to the position of the brake pedal, the following mechanism is provided. A small housing I88 is connected into the suction line between the cylinder I55 and the intake manifold 3I. Preferably, this housing is disposed in the suction line I83 at a point adjacent the intake manifold 3| so that the action of the valve means disposed therein will be quick and constant. This housing is provided with an opening I8I leading to the atmosphere, and between the opening I8I and the point of entrance of the suction line I83 into the housing, a valve seat I82 is formed. A valve I83 is adapted to rest against the seat I82 and is provided with an upwardly extending stem I84. Adjacent its top the stem is provided with a collar I85 secured against relative axial movement to the stem and against whicha washer I85bears. A coil spring I81 encircles the stem I84 and is held under compression between the washer I88 and a second washer I88 encircling the stem I84 and axially,

'slidable thereon. The compression of this spring I81 controls the point at which the suction within the tube I83 will cause the valve I83 to open,

and that when the valve I83 opens, air will be drawn into the-housing through the opening I8I,

' and thereby prevent'a higher degree of suction from being built up in the tube I83, and consequently'will limit the suction that may ,be applied to the cylinder I55.

The tension of the spring I81 is controlled in accordance'with the depression of the pedal I48 in the following manner. A bracket I89 is formed on the housing I88 and has pivotally connected thereto by means of a pin I98, a bell crank having a horizontally extending arm I9I and a vertically extending and I92. The free end of the arm I9I is provided with an upper curved face and is formed so asto receive the stem I84 within it, the upper curved face serving as a stop for limiting the downward movement of the washer I88 of the valve stem I84. The free end of the vertically extending arm I92 of the bell crank is connectedbymeans of a rod I93 tothe end of a downwardly extending arm I18 of the pedal I48.

The rod I93 preferably includes a turn buckle I94 for adjustably controlling the effective length of therod I93. It will be apparent that in this construction, the farther the pedal I48 is depressed, the higher the washer I88 will be moved on the stem I84 and consequently the greater will be the compression of the spring I81 and, ac-

detail in Fig. 3.

' pedal is returned to its normal rearward position is provided whereby excessive pressure within the hydraulic system will cause the admission of air .I95 is provided with an open end through which isinserted an expansible and contractible member I91, preferably of the metallic bellows type,

as illustrated. This bellows is provided with an outwardly extending flange I98 at its open end, which is clamped to'the housing I95 through a clamping ring I99, and thereby acts to seal the open end of the housing I95. The closed end of the bellows I91 is provided with a downwardly depending stem 288 which terminates in normally spaced but adjacent relationship with respect to the collar I85 provided on the stem I84 of valve I83.

In the above construction it will be apparent that the forces tending to move the valve I83 downwardly and thereby admit air in the vacuum system of the booster mechanism will be the degree of vacuumobtained in the suction line I83 and the pressure developed within the pressure line I48 of the hydraulicbraking system. The forcestending to oppose the opening of valve I83 will be the spring I81, the compression of which varies in accordance with the depression of pedal I48 and the tendency of the metallic bellows I91 to remain in extended position due to atmospheric pressure within its inner surface and the inherent tendency of the metallic bellows I91 to-remain in extendedposition. Thus, to open the valve I83, the suction within the line I83 must attain a sufiicient value, or the pressure within the fluid pressure line I48 must reach a certain value, or both, in order to overcome the compression of spring I81 conditioned in compression in accordance with the depression of pedal I48. The compression of spring I81, as previously pointed out,-

may be adjustably varied by means of a turn buckle I94.

It is also desired to provide in the present em able braking effort that may be applied by the booster mechanism, and such means is made adjustable and readily controllable by the driver from his normal driving position. To this end, a suction operated valveis connected by conduit 28I to the suction line I83 at a point relatively close to the intake manifold 3|. A check valve 81 isinterposed between the connection of conduit 28I and'conduit I83 to maintain the vacuum within the suction line of the booster mechanism at values corresponding to the higher degrees of vacuum developed within the intake manifold 3|. The construction of the suction operated valve may be the same as that disclosed relative to the previously described embodiment as shown in The limiting degree of the vacuum at which air will be admitted to the suction line of the booster mechanism and the application of the booster mechanism to the brakes released, is again under the control of the adjusting handle 15, readily accessible to the operator of the vehicle, and determined by the point to which this control handle is rotated.

As many changes could be made in-the above -bodiment, means for limiting the maximum avail- Y ing'mechanism by means of a suction line, a-

pedal connected to said mechanism for manually operating the same, a valve in communication with-saidline for limiting thedegree of suction which may be applied to said brake applying mechanism, a stem on said valve, an abutment slidably mounted on said stem, a second abutment on said stem flxed against movement in one direction, a spring mounted on said stem and interposed between said abutments, yieldable means for moving the first-mentioned abutment on said stem against the action of said spring, a

movement of the first-mentioned abutment against the action of the spring varying according to the movement of said pedal, a valve communicating with said suction line and operable independently of movement of said pedal for limiting the degree of suction obtainable in said line, and check valve means interposed in .said line adjacent said source of suction and said source and said valves for maintaining higher values of suction from said source in said line.

2. In a vehicle brake system, in combination, a suction operated brake applying mechanism, a

. source of suction connected to said brake applying mechanism by means of a suction line, means including a movable valve means for limiting the degree of suction which may be applied to said brake applying mechanism, spring means constantly urging said valve means toward one extremity of its movable position, a movable pedal, a cam connected to said pedal for simultaneous movement therewith, a yieldable member cooperating with said cam, an abutment for said spring controlled at least in part by said member, av

second valve communicating with said suction line adjacent said source of suction for limiting the degree of suction obtainable in said line independently of movement of said pedal.

3. In a vehicle brake system, in combination, a suction operated brake applying mechanism, a source of suction connected to said brake applying mechanism by means of a suction line, a valve for limiting the degree of suction which may be applied to said brake applying mechanism, biasing means constantly urging said valve toward one extremity of its movable position, a movable pedal, a cam adiustably connected to said pedal for simultaneous movement therewith, manual means for adjusting said cam relative to said pedal, a, yieldable member cooperating with said cam, an abutment for said spring controlled at least in part by said member, a

second valve communicating with said suction line for limiting the degree of suction obtainable therein independently of movement of said pedal. said valves communicating with said suction line at points close to said source of suction, and check valve means interposed in said suction line adjacent the source of suction and between said valves and said source.

-4. In a fluid pressure brake operating system for motor vehicles, a fluid pressure actuated brake applying element, a source oi dii'lerential of fluid pressure connected with said element by means of a conduit, a brake lever, a valve in communication with said conduit adjacent said source for controllingth transmittal of pressure therethrough, means carried by said lever for moving said valve, a second valve in said conduit.

biasing means engaging said second valve do! further controlling the transmittal of pressure through said conduit; a cam adiustably mounted relative to said lever, means for securing said cam in one of a plurality or adjusted positions, a yieldable connection between said cam and biasing means, and a third valve communicating with said conduit adjacentsaid source for further controlling the transmittal oi pressure to the conduit independently of movement of saidlever.

5. A brake system for an automotive vehicle comprising brakes for the individual wheels, means actuated by diflerential of fluid pressures for actuating the brakes, a valve for controlling the effective pressure exerted, a', brake vpedal,

means mechanically interconnecting the brake pedal and the brake, cam means secured to the brake pedal and being angularly' adjustable with respect to the pedal and further being operatively connected to the valve whereby to control the intensity oi the fluid pressure exerted upon the fluid pressure actuated. means and adjustable means ior limiting independently oi movement of the brake pedal, the effectiveness of the valve in order to prevent the development of differentials of pressure in the fluid pressure operated means in excess of a predetermined value, said last-named means being adjustable by the driver oi the vehicle. c

6. In a vehicle brake mechanism, a suction operated brake applying element, a source of suction connected thereto, a manually operable brake lever, means operable by said lever for variably limiting substantially in proportion to the extent that the lever is operated the degree of suction which may be built up in said element, said means including means interposed between said lever and said suction limiting means and adjustable with respect to said lever for varying the eil'ect of depression of the lever on said sue-'- tion limiting means, and manually controllable means independent of said first-named means for variably limiting the degree-o! suction which may be built up in said element.

I swear. r. moons. 

